液罐汽车直线制动稳定性的分析

对液罐汽车部分装载并直线制动时，罐内液体的质心坐标和制动稳定性进行分析讨论。部分装载的液罐汽车制动行驶时，其质心位置将向前、向上转移，使汽车的同步附着系数减小，造成后桥车轮先于前轴车轮抱死，致使后桥车轮侧向附着力下降而容易发生侧滑；同时还导致前后车轮抱死间隔时间增加。为了减小液罐汽车罐内液体质心的转移对汽车制动稳定性的影响，应在结构上采取措施，尽量控制罐内液体质心的转移量，提高同步附着系数。     

车顶行李架加载装置的气动力分析与试验

为了使车顶行李架的加载功能满足客户需求,需要在整车耐久试验过程中对其进行加载,验证其可靠性。文中选用两种加载装置对车顶行李架进行加载,利用ANSYS软件对两种装置在不同车速的气动阻力和气动升力进行分析;并以某SUV车型为研究对象,试验验证两种装置的可靠性和潜在失效模式。结果表明,车顶行李框更适合用于车顶行李架的耐久加载试验,为车顶行李架的加载试验提供指导。     

厢式货车的气动阻力及气动附加装置的应用

厢式货车在公路运输中发挥着越来越大的作用，研究厢式货车的减阻节能问题具有重要的意义，为此，对厢式货车空气阻力与油耗的关系，厢式货车的气动特性和各种气动附加装置的应用等问题进行了综述。     

气动汽车减压装置能耗及流场分析北大核心

以气动汽车减压装置为研究对象,运用Simulink对节流减压和容积减压装置减压过程可用能损耗进行仿真分析,并运用Fluent对节流减压和二级容积式减压过程进行流场分析。分析结果表明:节流减压装置减压过程可用能损耗高达27%~59%,在30MPa气源压力和3MPa出口压力的最常用工况下,能量损耗高达40%,能耗偏大;容积式减压较节流减压能耗损失减少了6%~22%,节能效果明显;节流减压装置减压过程较稳定,能稳定输出压力,节流效果明显;二级容积减压装置的第二级相对于第一级减压容器内气体压力场及速度场分布更均匀,减压过程更加稳定。     

大客车模型的气动特性研究

本文根据交通部新型豪华客运汽车－ＪＴ６１２０型大客车的均匀流缩尺模拟试验的结果，重点研究大客车的整体造型以及局部造型对气动阻力及各气动特性的影响；同时，探讨大客车表面压强分布的特有规律；提出大客车总体造型和布置以及减阻措施的可行途径。     

气动力地摩托车操纵稳定性的影响

空气作用于摩托车产生的气动力可分为气动阻力、气动侧向力和气动升力。气劝阻力直接影响摩托车动力性与经济怀；气劝侧向力和所动升力直接影响摩托车操纵稳定性及行驶安全性。改变摩托车外形可改变气动力大小、方向及作用点。     

计及车身附件气动干涉影响的汽车流场数值仿真研究

以降低汽车气动阻力、获得最优气动造型为目的,应用计算流体动力学方法对某轿车内外流场进行了数值仿真,分析并总结了车身附件气动干涉和发动机舱内空气流动对整车气动性能的影响.计算结果表明:车身附件对整车气动特性有较大影响.其中,底部结构和轮胎的影响较大;余者(后视镜、雨刮器和门把手)的影响很小.考虑了车身附件的影响后,气动阻力约增加23%;加上发动机舱内空气流动的影响,整车气动阻力共增大约35%.分析还表明,车轮的转动有利于改善车底气流与尾流的相互作用,使气动阻力稍有降低.     

刚性汽车的纵向极限稳定性分析

通过对刚性汽车进行受力分析,得到了刚性汽车发生纵翻的条件,并对汽车的纵向极限稳定性进行了分析,指出了提高汽车纵向稳定性的措施.     

Dynamics of Pneumatic Tire Vehicles with Connected Suspension Systems

A vehicle model, with 10 degrees of freedom is used to investigate the skidding conditions of any wheel of the vehicle in motion. Equations for the load transfer and equations for the pneumatic tire spring and shock absorber are derived. Parameters such as gradual cornering, U-curve cornering, the wavy road surface of different wave lengths and cases of independent and connected suspension systems are inputs to the system. The tire calculated forces and their corresponding maximum resistance forces are the outputs of the systems. A connected suspension system is found to resist skidding better than the independent suspension system. The system is non-linear, and numerical solutions are obtained.     

Dynamics of Pneumatic Tire Vehicles with Connected Suspension Systems

SUMMARY

A vehicle model, with 10 degrees of freedom is used to investigate the skidding conditions of any wheel of the vehicle in motion. Equations for the load transfer and equations for the pneumatic tire spring and shock absorber are derived. Parameters such as gradual cornering, U-curve cornering, the wavy road surface of different wave lengths and cases of independent and connected suspension systems are inputs to the system. The tire calculated forces and their corresponding maximum resistance forces are the outputs of the systems. A connected suspension system is found to resist skidding better than the independent suspension system. The system is non-linear, and numerical solutions are obtained.     

Optimization of the Lateral Stability of Rail Vehicles

Summary The lateral stability of a rail vehicle is optimized using a combination of multibody dynamics, sequential quadratic programming, and a genetic algorithm. Several steps are taken to validate this integrated approach and to show its effectiveness. First, a hand-derived solution to a 17 degree of freedom linear rail vehicle model is compared to the simulation results from the A'GEM multibody dynamics software. Second, the calculation of the ‘critical speed’ (above which a rail vehicle response becomes unstable) using sequential quadratic programming is validated for a specific example. In the process, the existence of sharply-discontinuous ‘cliffs’ in the plots of critical speed versus suspension stiffnesses are identified. These cliffs, which are due to switching of the least-damped mode in the system, greatly hinder the application of gradient-based optimization methods. Two methods that do not require gradient information, a genetic algorithm and the Nelder-Mead's Simplex algorithm, are used to optimize the critical speed. The two algorithms and their results are compared. In recognition of the cliff phenomenon, the definition of critical speed is generalized to make it a more practical measure of lateral stability.     

Optimization of the Lateral Stability of Rail Vehicles

Summary The lateral stability of a rail vehicle is optimized using a combination of multibody dynamics, sequential quadratic programming, and a genetic algorithm. Several steps are taken to validate this integrated approach and to show its effectiveness. First, a hand-derived solution to a 17 degree of freedom linear rail vehicle model is compared to the simulation results from the A'GEM multibody dynamics software. Second, the calculation of the 'critical speed' (above which a rail vehicle response becomes unstable) using sequential quadratic programming is validated for a specific example. In the process, the existence of sharply-discontinuous 'cliffs' in the plots of critical speed versus suspension stiffnesses are identified. These cliffs, which are due to switching of the least-damped mode in the system, greatly hinder the application of gradient-based optimization methods. Two methods that do not require gradient information, a genetic algorithm and the Nelder-Mead's Simplex algorithm, are used to optimize the critical speed. The two algorithms and their results are compared. In recognition of the cliff phenomenon, the definition of critical speed is generalized to make it a more practical measure of lateral stability.     

Lateral Stability of Towed Flexible Vehicles

The highway transport of mobile homes is a matter of concern for the increasingly safety-minded driving public. The low speeds of towed vehicles necessary to maintain stability, together with the requirements for excessive lane widths due to clearance for the lateral motion, result in increased likelihood of traffic accidents, impeded traffic flow, and reduced highway capacity. A safe increase in the stable cruising speed, coupled with a decreased amplitude in the pendular motion helps alleviate all three of the aforementioned problems. Energy input at hitch point and lateral forces between the road and tires permit lateral vehicular motions, which occur above a critical speed, to increase in amplitude until possibly a limit cycle or instability is reached. One would expect that structural dynamics could have a pronounced influence on the lateral response of towed vehicles with large and relatively flexible chassis, such as mobile homes. The objective of this research is to determine the influence of chassis structural parameters on the lateral stability of towed flexible bodies during transport. The mass of the towing vehicle is assumed infinitely large, thus eliminating any dynamic interconnection between the towing and towed vehicles. The assumed modes method is used to describe the lateral deflection of the flexible towed vehicle. Results of the study of this model indicate that increase in structural rigidity of towed vehicle increases the critical towing speed whereas increase in the tire cornering coefficient reduces the safe towing speed, which is true only for this simplified model where the dynamic interaction with the towing vehicle is not included.     

Iveco在RAI阿姆斯特丹上的全明星阵容

Iveco公司参加了第28届阿姆斯特丹国际汽车展,该展览是欧洲最重要的道路运输设备展之一,展会日期为2005年10月13—22日。     

Overturning Stability of Three Wheeled Motorized Vehicles

Three wheeled motorized vehicles are a major mode of public transport in many countries. These vehicles are prone to overturning even during normal turning and obstacle avoidance maneuvers. This paper presents a parametric analysis of a mathematical model of the vehicle and evolves guidelines for improving the overturning stability in terms of vehicle geometry and suspension properties.

Differential equations governing the dynamic behavior of the vehicle are derived on the basis of a six degree of freedom model. The vehicle response to variations in steering, engine power and braking inputs is then numerically simulated. The effects of vehicle geometry and elasto-damping suspension coefficients on the vehicle stability are presented. The results indicate an optimum position of the center of gravity where the vehicle is most stable. While stiffer suspensions favour stability, there exists an optimum value of suspension damping for which the minimum wheel load is a maximum.     

Stability and Riding Quality of Railway Vehicles

The so-called critical speed of a linearized railway vehicle is shown to be no useful measure for the stability of the system in practice. The important interaction between vehicle and track can be taken into account by the riding quality for a certain vehicle on every particular piece of track. The riding quality is determined by the accelerations transmitted to the payload, weighted according to comfort standards, and the relative displacements between wheel and rail. From the riding quality demands both for vehicle design and for maintenance of the track can be derived.